The Co Longford factory severely damaged by fire on Sunday is due to partly re-open in the next two to three weeks, Siptu said today.
The move was confirmed at a meeting this morning between the union and management at C&D Foods.
Afterwards, Siptu Longford/Westmeath branch organiser, Seamus McNamee said: "This is a positive outcome for those workers employed in the soft food section of the plant.
"We will continue to work closely with management and the members to see what else can be done."
Over150 people were employed in the soft food section before the fire, though a specific number for those who will be able to return to work following today's development has not been established.
Management will be making further contact with their customers and will meet Siptu next week.
It is understood management are considering a number of options, including outsourcing production while the factory is rebuilt.
Workers will be updated on developments at a general meeting in the Lonford Arms Hotel hoseted by management.
It is unknown how many of the jobs can be saved in the longer term after Sunday's fire which badly damaged the Edgeworthstown factory. Gardaí have ruled out arson as the cause of the fire.
Management surveyed the damage yesterday and held meetings with insurers and financiers to examine the possibility of reopening the factory, which produced some 160 million cans of pet food last year. Existing stocks will run out in less than two weeks.
Around 450 workers who were temporarily laid off after the fire today began the process of signing on for social welfare benefits.
The Department of Social and Family Affairs set up special information meetings to make staff aware of their entitlements. Fás are also examining the possibility of setting up a skills-enhancement programme to assist those who are made redundant.
C&D Foods, which had annualised sales of €100 million, is managed by Philip Reynolds, son of the former taoiseach Albert Reynolds, who set up the company in 1969.